In general, various source materials such as crude oil are often present as a mixture of numerous chemicals. Therefore, the source materials themselves are hardly used in industries, but are generally separated into respective compounds that are used in industries. A distillation process is representative of chemical processes for separating a mixture.
In general, the distillation process serves to separate the mixture into two components: a high boiling point component and a low boiling point component. Therefore, the distillation columns whose number (n−1) is smaller than the number (n) of components in the mixture to be separated by 1 are used. That is to say, a process of separating a three-component mixture has mainly used a structure in which two distillation columns are continuously operated on site in conventional distillation industries.
A conventional distillation process of separating a three-component mixture is shown in FIG. 1.
The conventional distillation process uses a two-column system in which a lowermost boiling point component (D) is separated in a first column 11, and a middle boiling point component (S) and a high boiling point component (B) are separated in a second column 21.
In a conventional two-column distillation system which is a conventional process of distilling alcohols, a compositional profile in a first column is shown in FIG. 2. As shown in FIG. 2, the middle boiling point component (S) may be generally remixed in a lower section of the first column. In particular, a compositional profile in the first column when octanol such as 2-ethyl hexanol is separated as the middle boiling point component is shown in FIG. 3. As shown in FIG. 3, it can be seen that the octanol may be remixed in the lower section of the first column.
The above-described conventional distillation process can easily control a composition of a product, but the middle boiling point component is remixed in the first distillation column. Therefore, a thermodynamic efficiency in the distillation column is degraded, resulting in unnecessary consumption of energy.
In order to solve these problems, much research on a new distillation structure has been conducted. A representative example of improving a separation efficiency using a thermally coupled structure may be a structure of a Petlyuk distillation column as shown in FIG. 4. The Petlyuk distillation column is arranged in a structure in which a preliminary separator 12 and a main separator 22 are thermally coupled. Therefore, a low boiling point component and a high boiling point component are primarily separated in the preliminary separator, and then flow to a feed plate of the main separator through a column-top portion and a column-bottom portion of the preliminary separator. Thereafter, the low boiling point, middle boiling point, and high boiling point components are separated in the main separator. This structure has high energy efficiency since a distillation curve in the Petlyuk distillation column is similar to an equilibrium distillation curve. However, the design and operation of a process are not easy, and the balance of pressure in the distillation column is particularly difficult to adjust.
In order to solve the problems regarding the Petlyuk distillation column, a dividing wall distillation column (DWC) has been proposed. A thermodynamic aspect of the DWC is similar to that of the Petlyuk distillation column, but a structural aspect is different from that of the Petlyuk distillation column in that a dividing wall is installed in a distillation column to integrate the preliminary separator of the Petlyuk distillation column in the main separator. Such a structure is highly advantageous in that operations are easily performed since the problems regarding the balance between the preliminary separator of the Petlyuk distillation column and the main separator are naturally solved and thus operations are simple, and the investment costs may also be significantly reduced since two types of distillation columns are integrated into one.
Korean Patent No. 080482 filed by and issued to this applicant discloses a conventional technique associated with the refinement of 2-ethyl hexanol.
The above-described technique relates to a purification method including passing a byproduct, which is generated in a plant for preparing 2-ethyl hexanol from butylaldehyde through an aldol condensation reaction and a hydrogenation reaction, through two multi-stage distillation columns to recover 2-ethyl hexanol and 2-ethylhexyl-2-ethyl hexanoate, characterized in that the byproduct includes 100 parts by weight of 2-ethyl hexanol, 2 to 6 parts by weight of a butylaldehyde trimer, 7 to 12 parts by weight of 2-ethylhexyl-2-ethyl hexanoate and 0.01 to 0.3 parts by weight of a high boiling point component, and the method includes passing the by-product through a first multi-stage distillation column to recover 2-ethyl hexanol and distilling a residual substance in a second multi-stage distillation column under the operating conditions such as an operating pressure of 980.665 to 9806.650 kPa and an operating temperature of 150 to 200° C. to recover 2-ethylhexyl-2-ethyl hexanoate.
Such a technique uses two columns like conventional processes, but the present invention is quite different from this technique in that it is not directed to a distillation column including a dividing wall.